Towards a Precision Cosmology from Starburst Galaxies at z>2

This work investigates the use of a well-known empirical correlation between the velocity dispersion, metallicity, and luminosity in H beta of nearby HII galaxies to measure the distances to HII-like starburst galaxies at high redshifts. This correlation is applied to a sample of 15 starburst galaxies with redshifts between z=2.17 and z=3.39 to constrain Omega_m, using data available from the literature. A best-fit value of Omega_m = 0.21 +0.30 -0.12 in a Lambda-dominated universe and of Omega_m = 0.11 +0.37 -0.19 in an open universe is obtained. A detailed analysis of systematic errors, their causes, and their effects on the values derived for the distance moduli and Omega_m is carried out. A discussion of how future work will improve constraints on Omega_m by reducing the errors is also presented.Comment: 7 pages, 3 figures, accepted for publication in MNRA

Physical properties of outflows: Comparing CO and H2O based parameters in Class 0 sources

Context. The observed physical properties of outflows from low-mass sources put constraints on possible ejection mechanisms. Historically, these quantities have been derived from CO using ground-based observations. It is thus important to investigate whether parameters such as momentum rate (thrust) and mechanical luminosity (power) are the same when different molecular tracers are used. Aims. We aim at determining the outflow momentum, dynamical time-scale, thrust, energy and power using CO and H2O as tracers of outflow activity. Methods. Within the framework of the WISH key program, three molecular outflows from Class 0 sources have been mapped using the HIFI instrument aboard Herschel. We use these observations together with previously published H2 data to infer the physical properties of the outflows. We compare the physical properties derived here with previous estimates based on CO observations. Results. Inspection of the spatial distribution of H2O and H2 confirms that these molecules are co-spatial. The most prominent emission peaks in H2 coincide with strong H2O emission peaks and the estimated widths of the flows when using the two tracers are comparable. Conclusions. For the momentum rate and the mechanical luminosity, inferred values are independent of which tracer that is used, i.e., the values agree to within a factor of 4 and 3 respectively.Comment: Accepted for publication in A&A, 5 pages, 2 figure

Quantifying offshore fore-arc deformation and splay-fault slip using drowned Pleistocene shorelines, Arauco Bay, Chile

Indexación: Web of Science; Scopus.Most of the deformation associated with the seismic cycle in subduction zones occurs offshore and has been therefore difficult to quantify with direct observations at millennial timescales. Here we study millennial deformation associated with an active splay-fault system in the Arauco Bay area off south central Chile. We describe hitherto unrecognized drowned shorelines using high-resolution multibeam bathymetry, geomorphic, sedimentologic, and paleontologic observations and quantify uplift rates using a Landscape Evolution Model. Along a margin-normal profile, uplift rates are 1.3 m/ka near the edge of the continental shelf, 1.5 m/ka at the emerged Santa María Island, −0.1 m/ka at the center of the Arauco Bay, and 0.3 m/ka in the mainland. The bathymetry images a complex pattern of folds and faults representing the surface expression of the crustal-scale Santa María splay-fault system. We modeled surface deformation using two different structural scenarios: deep-reaching normal faults and deep-reaching reverse faults with shallow extensional structures. Our preferred model comprises a blind reverse fault extending from 3 km depth down to the plate interface at 16 km that slips at a rate between 3.0 and 3.7 m/ka. If all the splay-fault slip occurs during every great megathrust earthquake, with a recurrence of ~150–200 years, the fault would slip ~0.5 m per event, equivalent to a magnitude ~6.4 earthquake. However, if the splay-fault slips only with a megathrust earthquake every ~1000 years, the fault would slip ~3.7 m per event, equivalent to a magnitude ~7.5 earthquake. ©2017. American Geophysical Union.http://onlinelibrary.wiley.com/doi/10.1002/2016JB013339/epd

Metabolism of Nonessential N15-Labeled Amino Acids and the Measurement of Human Whole-Body Protein Synthesis Rates

Eight N-15 labeled nonessential amino acids plus (15)NH4Cl were administered over a 10 h period to four healthy adult males using a primed-constant dosage regimen. The amount of N-15 excreted in the urine and the urinary ammonia, hippuric acid, and plasma alanine N-15 enrichments were measured. There was a high degree of consistency across subjects in the ordering of the nine compounds based on the fraction of N-15 excreted (Kendall coefficient of concordance W = 0.83, P is less than 0.01). Protein synthesis rates were calculated from the urinary ammonia plateau enrichment and the cumulative excretion of N-15. Glycine was one of the few amino acids that gave similar values by both methods

The Molecular Interstellar Medium in Ultraluminous Infrared Galaxies

We present CO observations of a large sample of ultraluminous IR galaxies out to z = 0.3. Most of the galaxies are interacting, but not completed mergers. All but one have high CO(1-0) luminosities, log(Lco [K-km/s-pc^2]) = 9.92 +/- 0.12. The dispersion in Lco is only 30%, less than that in the FIR luminosity. The integrated CO intensity correlates Strongly with the 100 micron flux density, as expected for a black body model in which the mid and far IR radiation are optically thick. We use this model to derive sizes of the FIR and CO emitting regions and the enclosed dynamical masses. Both the IR and CO emission originate in regions a few hundred parsecs in radius. The median value of Lfir/Lco = 160 Lsun/(K-km/s-pc^2), within a factor of two of the black body limit for the observed FIR temperatures. The entire ISM is a scaled up version of a normal galactic disk with densities a factor of 100 higher, making even the intercloud medium a molecular region. Using three different techniques of H2 mass estimation, we conclude that the ratio of gas mass to Lco is about a factor of four lower than for Galactic molecular clouds, but that the gas mass is a large fraction of the dynamical mass. Our analysis of CO emission reduces the H2 mass from previous estimates of 2-5e10 Msun to 0.4-1.5e10 Msun, which is in the range found for molecular gas rich spiral galaxies. A collision involving a molecular gas rich spiral could lead to an ultraluminous galaxy powered by central starbursts triggered by the compression of infalling preexisting GMC's.Comment: 34 pages LaTeX with aasms.sty, 14 Postscript figures, submitted to ApJ Higher quality versions of Figs 2a-f and 7a-c available by anonymous FTP from ftp://sbast1.ess.sunysb.edu/solomon/

Radiative Transfer Effects in He I Emission Lines

We consider the effect of optical depth of the 2 ^{3}S level on the nebular recombination spectrum of He I for a spherically symmetric nebula with no systematic velocity gradients. These calculations, using many improvements in atomic data, can be used in place of the earlier calculations of Robbins. We give representative Case B line fluxes for UV, optical, and IR emission lines over a range of physical conditions: T=5000-20000 K, n_{e}=1-10^{8} cm^{-3}, and tau_{3889}=0-100. A FORTRAN program for calculating emissivities for all lines arising from quantum levels with n < 11 is also available from the authors. We present a special set of fitting formulae for the physical conditions relevant to low metallicity extragalactic H II regions: T=12,000-20,000 K, n_{e}=1-300 cm^{-3}, and tau_{3889} < 2.0. For this range of physical conditions, the Case B line fluxes of the bright optical lines 4471 A, 5876 A, and 6678 A, are changed less than 1%, in agreement with previous studies. However, the 7065 A corrections are much smaller than those calculated by Izotov & Thuan based on the earlier calculations by Robbins. This means that the 7065 A line is a better density diagnostic than previously thought. Two corrections to the fitting functions calculated in our previous work are also given.Comment: To be published in 10 April 2002 ApJ; relevant code available at ftp://wisp.physics.wisc.edu/pub/benjamin/Heliu

Detection and Mapping of Decoupled Stellar and Ionized Gas Structures in the Ultraluminous Infrared Galaxy IRAS 12112+0305

Integral field optical spectroscopy with the INTEGRAL fiber-fed system and HST optical imaging are used to map the complex stellar and warm ionized gas structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images reconstructed from wavelength-delimited extractions of the integral field spectra reveal that the observed ionized gas distribution is decoupled from the stellar main body of the galaxy, with the dominant continuum and emission-line regions separated by projected distances of up to 7.5 kpc. The two optical nuclei are detected as apparently faint emission-line regions, and their optical properties are consistent with being dust-enshrouded weak-[OI] LINERs. The brightest emission-line region is associated with a faint (m_{I}= 20.4), giant HII region of 600 pc diameter, where a young (about 5 Myr) massive cluster of about 2 $\times$ 10$^7$ $M_{\odot}$ dominates the ionization. Internal reddening towards the line-emitting regions and the optical nuclei ranges from 1 to 8 magnitudes, in the visual. Taken the reddening into aacount, the overall star formation in IRAS 12112+0305 is dominated by starbursts associated with the two nuclei and corresponding to a star formation rate of 80 $M_{\odot}$ yr$^{-1}$.Comment: 2 figures, accepted to Ap.J. Letter

UV Interstellar Absorption Lines towards the Starburst Dwarf Galaxy NGC 1705

Archival Goddard High Resolution Spectrograph low-resolution spectra of NGC 1705, with wavelength ranges 1170.3 to 1461.7 A and 1453.5 to 1740.1 A and a velocity resolution of about 100 km\s, have been used to derive the velocity structure and equivalent widths of the absorption lines of Si II 1190.42, 1260.42, 1304.37 and 1526.71 A, S II 1253 , Al II 1670.79 Aand Fe II 1608.45 A in this sightline. Three relatively narrow absorption components are seen at LSR velocities --20 km/s, 260 km/sand 540 km/s. Arguments are presented to show these absorption features are interstellar rather than stellar in origin based on a comparison with the C III 1175.7 A absorption feature. We identify the --20 km/s component with Milky Way disk/halo gas and the 260 km/s component with an isolated high-velocity cloud HVC 487. This small HVC is located about 10 degrees from the H I gas which envelops the Magellanic Clouds and the Magellanic Stream (MS). The (Si/H) ratio for this HVC is > 0.6 (Si/H)solar which together with velocity agreement, suggests association with the Magellanic Cloud and MS gas. H-alpha emission line kinematics of NGC 1705 show the presence of a kpc-scale expanding supershell of ionized gas centered on the central nucleus with a blue-shifted emission component at 540 km/s (Meurer et al. 1992). We identify the 540 km/s absorption component seen in the GHRS spectra with the front side of this expanding, ionized supershell. The most striking feature of this component is strong Si II and Al II absorption but weak Fe II 1608 A absorption. The low Fe II column density derived is most likely intrinsic since it cannot be accounted for by ionization corrections or dust depletion. Due to their shallow gravitational potential wells, dwarf galaxies have small gravitational binding energies and are vulnerable to largeComment: 15 pages, LaTEX, 1 figure. Accepted for publication in Astrophysical Journal Letter

ASCA Observation of an X-Ray-Luminous Active Nucleus in Markarian 231

We have obtained a moderately long (100 kilosecond) ASCA observation of the Seyfert 1 galaxy Markarian 231, the most luminous of the local ultraluminous infrared galaxy (ULIRG) population. In the best-fitting model we do not see the X-ray source directly; the spectrum consists of a scattered power-law component and a reflection component, both of which have been absorbed by a column N_H \approx 3 X 10^(22)/cm^2. About 3/4 of the observed hard X-rays arise from the scattered component, reducing the equivalent width of the iron K alpha line. The implied ratio of 1-10 keV X-ray luminosity to bolometric luminosity, L_x/L_bol \sim 2%, is typical of Sy 1 galaxies and radio-quiet QSOs of comparable bolometric luminosities, and indicates that the bolometric luminosity is dominated by the AGN. Our estimate of the X-ray luminosity also moves Mrk 231 in line with the correlations found for AGN with extremely strong Fe II emission. A second source separated by about 2 arcminutes is also clearly detected, and contributes about 25% of the total flux.Comment: 11 pages, 3 figures; to appear in ApJ Letter

Spitzer Observations of CO2 Ice Towards Field Stars in the Taurus Molecular Cloud

We present the first Spitzer Infrared Spectrograph observations of the 15.2 micron bending mode of CO2 ice towards field stars behind a quiescent dark cloud. CO2 ice is detected towards 2 field stars (Elias 16, Elias 3) and a single protostar (HL Tau) with anabundance of ~15-20% relative to water ice. CO2 ice is not detected towards the source with lowest extinction in our sample, Tamura 17 (A_V = 3.9m). A comparison of the Elias 16 spectrum with laboratory data demonstrates that the majority of CO2 ice is embedded in a polar H2O-rich ice component, with ~15% of CO2 residing in an apolar H2O-poor mantle. This is the first detection of apolar CO2 towards a field star. We find that the CO2 extinction threshold is A_V = 4m +/- 1m, comparable to the threshold for water ice, but significantly less than the threshold for CO ice, the likely precursor of CO2. Our results confirm CO2 ice forms in tandem with H2O ice along quiescent lines of sight. This argues for CO2 ice formation via a mechanism similar to that responsible for H2O ice formation, viz. simple catalytic reactions on grain surfaces.Comment: Accepted by Astrophysical Journal Letter